Nodari et al. have discovered a major new class of molecules that activate the accessory olfactory (vomeronasal) system: sulfated steroids. Vomeronasal sensory neurons (VSNs) detect cues that are important for social communication. Mouse urine strongly activates VSNs, but few of its active compounds had been identified. Using fractionation, mass spectrometry, and multielectrode physiological recordings, Nodari et al. found that sulfated steroids account for 80% of the vomeronasal-stimulating activity in female urine. Testing synthetic steroids revealed that individual neurons responded selectively and with different sensitivity to one to four closely related compounds, but, as a population, VSNs detected all classes of steroid hormones known to control mammalian physiology. Sulfation is thought to help clear steroids from the body, and the levels of sulfated corticosterone increased following restraint stress, suggesting that urine levels of sulfated hormones reflect the recent physiological state. Interestingly, sulfated steroids were not detected in males, suggesting another major class ofVSNstimuli remains undiscovered.
Major New Class of Vomeronasal Stimuli
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